The first was formed on 1 October 1914 for service with the 3rd Cavalry Division and commanded C, G and K Batteries, RHA.

XV Brigade, RHA was formed at Leamington, Warwickshire in January 1915 with:[4] On formation, the batteries were re-equipped with four 18 pounders each.

[8] The division started landing at Cape Helles from 7am on 25 April and served on the Gallipoli Peninsula until January 1915.

From 16 August to the night of 19/20 December 1915, the bulk of the division served at Suvla but the brigade remained at Helles.

[11] Still with 29th Division, the brigade advanced into Germany to take part in the Occupation of the Rhineland.

[9] It left 29th Division in December 1918 and returned to England from Germany in April 1919.